Method and system for loading pressurized compressed natural gas on a floating vessel

Abstract

The method for loading pressurized compressed natural gas into a storage element on a floating vessel entails introducing compressed natural gas from a source into a storage element located on the floating vessel raising the storage element pressure from about 800 psi to about 1200 psi at an ambient temperature; allowing a portion of the compressed natural gas to cool forming a liquid in the storage element; removing remaining vapor phase compressed natural gas from the storage element to a refrigeration plant, wherein the refrigeration plant is adapted to cool the vapor; removing the liquid from the storage element to the refrigeration plant; wherein the refrigeration plant is adapted to cool the liquid; mixing the cooled vapor phase with the cooled liquid phase and returning the mixture to the storage element; repeating the steps until the vapor has been cooled and is substantially a liquid.

1. A method for loading pressurized compressed natural gas into a storage element on a floating vessel comprising the steps of:
 a. introducing compressed natural gas from a source into a storage element located on the floating vessel raising the storage element pressure to about 800 psi to about 1200 psi at an ambient temperature; 
 b. allowing a portion of the compressed natural gas to cool forming a liquid in the storage element; 
 c. removing remaining vapor phase compressed natural gas from the storage element to a refrigeration plant, wherein the refrigeration plant is adapted to cool the vapor; 
 d. removing the liquid from the storage element to the refrigeration plant; wherein the refrigeration plant is adapted to cool the liquid; 
 e. mixing the cooled vapor phase with the cooled liquid phase and returning the mixture to the storage element; and 
 f. repeating steps (c) through (e) until the vapor has been cooled and is substantially a liquid. 
 
     
     
       2. The method of  claim 1 , further comprising the step of ballasting the floating vessel on one end in order to orientate the storage element on an incline. 
     
     
       3. The method of  claim 1 , wherein the source is located on a land-based facility, a floating facility, a platform-based facility, or combinations thereof. 
     
     
       4. The method of  claim 1 , wherein the refrigeration plant is located on a land-based facility, a floating facility, a platform-based facility, or combinations thereof. 
     
     
       5. The method of  claim 1 , wherein the step of flowing the vapor mixture from the storage element to the refrigeration plant is completed using a gas compressor. 
     
     
       6. The method of  claim 1 , wherein the storage element is a double-walled tubular member comprising an inner load bearing wall, an outer wall, and an insulating layer. 
     
     
       7. The method of  claim 6 , wherein the inner load bearing wall is constructed of a low-alloy steel comprising about 3.5 wt % or less of nickel, wherein the low-alloy steel improves tensile strength of the inner load bearing wall to 115 ksi or less. 
     
     
       8. The method of  claim 6 , wherein the inner load bearing wall comprises a diameter ranging from about 8 feet to about 15 feet. 
     
     
       9. The method of  claim 6 , wherein the outer wall is a steel, stainless steel, an aluminum, a thermoplastic, a fiberglass, or combinations thereof. 
     
     
       10. The method of  claim 6 , wherein the outer wall comprises a diameter that is up to four feet larger in diameter than the inner wall. 
     
     
       11. The method of  claim 6 , wherein the insulating layer is perlite.